1. Field of the Invention
This invention relates to a chelating composition formed of a specific aliphatic polycarboxylic acid and sugar or saccharic acid. More specifically, this invention relates to a chelating composition which can be advantageously used as an agent for preventing the precipitation of a metal ion contained in cooling water for use in a cooling tower, water for use in a boiler, and the like; an agent for repressing the formation of smear on cloth due to the sedimentation of a metal ion on a cloth during the dyeing or bleaching treatment; and an additive for a fiber processing agent, a detergent in food manufacturing industry, a detergent in a chemical plant, a metal surface-treating agent, and a paper-pulp processing agent.
This invention also relates to a chelating composition to be used in a detergent for cleansing and removing stain adhering to a hard surface of glass, plastic, or metal. More specifically, this invention relates to a chelating composition to be used in a detergent which is used for cleansing and removing stain adhering to a hard surface of a package encasing provisions such as beverage and processed food, a container accommodating a package, and a pipe, a tank, a sterilizing plate, and a filling device in foodstuff production facilities by such means as immersion in, circulation and spray application of a liquid detergent, and to a chelating composition to be used in a chemical-mechanical industry grade detergent which is used for metal surface cleansing, metal cleansing, and precision cleansing. Particularly, this invention relates to a chelating composition to be used in a detergent which exhibits high cleansing power on a hard surface and, at the same time, excels in n biodegradability.
2. Description of the Related Art
Agents which are used in cleansing, dyeing, bleaching, and other various treatments given to fibers in the textile industry have incurred possibilities that their actions are obstructed by metal ions (particularly calcium ions and iron ions) contained in water. When a peroxide is used in the bleaching treatment in the presence of a metal ion, not only the metal ion promotes the decomposition of the peroxide and prevent the peroxide from manifesting satisfactory bleaching effects on a cloth but also the hydroxide of the metal ion settles possibly to such an extent as of inducing formation of smear on a cloth.
A metal ion has also incurred a possibility that when present in cooling water for a cooling tower or in water for a boiler, it will settle and eventually clog the pipe.
For the purpose of repressing the sedimentation of such a metal ion, numerous chelating agents such as, for example, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), N-(hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA), diethylenetriaminepentaacetic acid (DTPA), and polyphosphoric acid have been used.
Many of these chelating agents, while exhibiting an excellent ability to sequester metal ions, are not easily subjected to biodegradation. They incur possibilities that their plant effluents, when discharged without any treatment into the neighboring environment, will cause water pollution. Even when an activated sludge is used to treat a chelating agent, it cannot be expected to purge the effluents of the chelating agent, and therefore all possible efforts must be made to recover the chelating agent from the effluent. Further, the chelating agent itself possibly forms a cause for eutrophication and induces abnormal growth of microorganisms.
It has been known that particularly an iron ion, among other metal ions, tends to settle as a hydroxide at high pH levels. No existing chelating agents, however, have been proposed which are capable of sequestering iron ions at a high pH level and preventing them from settling.
Recently, the amounts of production of provisions such as beverages and processed foods have been steadily growing year after year and the varieties of these provisions have been diversifying as well. The hygienic quality controls imposed on the provisions, consequently, have been gaining in severity. Particularly, the trend of the provisions toward diversification of variety has been enhancing the chances of necessitating changes in variety. As a result, the foodstuff production facilities have been inevitably compelled to undergo frequent cleaning. This cleaning of the production facilities has heretofore resorted to a procedure which comprises dismantling a given production facilities, immersing the separated parts in a cleansing liquid, and rubbing them therein as with a brush.
In consequence of the dimensional growth of production facilities and the increase in frequency of the cleaning which are prevalent in recent years, however, the cleaning of these production facilities by the procedure involving such steps as dismantling and rubbing has become difficult because it calls for so much time and labor as to boost the cost of production to a prohibitive extent. In these circumstances, such methods as a procedure of circulation cleaning which consists in circulating a cleansing liquid through production facilities wished to be cleaned and a procedure of stationary cleaning (CIP) which consists in cleansing and removing stain adhering to a surface having a large area such as of a tank by spraying a cleansing liquid thereto have been adopted recently in place of the method as mentioned above.
Accompanying the growing trend of provisions toward the diversification of variety mentioned above, plastic, metal, and various other materials have come to be adopted in addition to the conventional glass materials for the packages of provisions. The diversification of materials for packages and the diversification of shapes of packages entail possibilities that the conventional cleansing liquid would fail to cleanse and remove stain sufficiently. Further, in recent years, owing to the uplift of the spirit for the protection of the environment, the glass packages whose reuse for the sake of contribution to the recycle of natural resources has come to induce revival of attention, like other reusable packages, have been urging the development of a detergent having a sufficient cleansing power to cleanse and remove stain of metal, adhesive agent, etc. eluting from a label in addition to the conventional stain.
As detergents for use in the circulation cleaning or stationary cleaning of production facilities as mentioned above or in the cleaning of packages, it has been heretofore customary to use an aqueous detergent solution containing 1 to 3% by weight of an alkali metal hydroxide and 0.2 to 0.4% by weight of an alkali metal salt of ethylenediaminetetraacetic acid (chelating compound). The detergents which use a surfactant as a main component, contain additionally such an alkali salt as carbonate, silicate, or phosphate which has relatively weak alkalinity, and an alkali metal salt of aspartic acid-N,N-diacetic acid, and find utility mainly in household applications have been also known (see EP-A-513,948, U.S. Pat. No. 3,637,511, and DE-B-2,220,295).
Although the aforementioned aqueous detergent solution containing the alkali metal salt of ethylenediaminetetraacetic acid indeed excels in the ability to cleanse and remove stain adhering to a surface of production facilities and packages, it suffers deficiency in the biodegradability. It, therefore, is not necessarily desirable from the viewpoint of the existent environmental protection to use this aqueous detergent solution in a foodstuff production plant, because the waste of this solution discharged from the plant undergoes no satisfactory biodegradation by the conventional treatment with activated sludge.
As mentioned above, numerous studies have been contemplated for developing a composition which combines a strong detergent power with excellent biodegradability. None of the compositions developed to date fully reconcile the capacity for detergency and the biodegradability.